U.S. patent number 8,592,699 [Application Number 12/860,547] was granted by the patent office on 2013-11-26 for single support lever keyboard mechanism.
This patent grant is currently assigned to Apple Inc.. The grantee listed for this patent is Bradley Joseph Hamel, Patrick Kessler, James J. Niu. Invention is credited to Bradley Joseph Hamel, Patrick Kessler, James J. Niu.
United States Patent |
8,592,699 |
Kessler , et al. |
November 26, 2013 |
Single support lever keyboard mechanism
Abstract
A keyboard mechanism for a low-travel keyboard and methods of
fabrication are described. The low-travel keyboard is suitable for
a thin-profile computing device, such as a laptop computer, netbook
computer, desktop computer, etc. The keyboard includes a key cap
that can be formed of a variety of materials in the form of a flat
slab. The key cap is attached to one end of a support lever that
supports it from underneath. In one embodiment, the support lever
is formed of a rigid material and is pivotally coupled with a
substrate on the other end. In another embodiment, the support
lever is formed of a flexible material and is fixedly attached to
the substrate on the other end. The portion of the support lever
that is attached to the key cap is positioned over a metal dome
that can be deformed to activate the switch circuitry of the
membrane on printed circuit board underneath the dome.
Inventors: |
Kessler; Patrick (San
Francisco, CA), Hamel; Bradley Joseph (Sunnyvale, CA),
Niu; James J. (San Jose, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Kessler; Patrick
Hamel; Bradley Joseph
Niu; James J. |
San Francisco
Sunnyvale
San Jose |
CA
CA
CA |
US
US
US |
|
|
Assignee: |
Apple Inc. (Cupertino,
CA)
|
Family
ID: |
45593199 |
Appl.
No.: |
12/860,547 |
Filed: |
August 20, 2010 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20120043191 A1 |
Feb 23, 2012 |
|
Current U.S.
Class: |
200/5A;
200/343 |
Current CPC
Class: |
H01H
3/125 (20130101); H01H 2223/014 (20130101); Y10T
29/49105 (20150115); H01H 2223/058 (20130101) |
Current International
Class: |
H01H
9/26 (20060101); H01H 13/70 (20060101) |
Field of
Search: |
;200/5A,341-345,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Balakrishnan, et al., "Keyswitch Orientation Can Reduce Finger
Joint Torques During Tapping on a Computer Keyswitch," Harvard
School of Public Health, Boston, Massachusetts, 2006. cited by
applicant .
Ecker, "Keyboard with Toggled Cantilever," IBM TDB, Sep. 1, 1970.
cited by applicant.
|
Primary Examiner: Chung Trans; Xuong
Attorney, Agent or Firm: Brownstein Hyatt Farber Schreck,
LLP
Claims
What is claimed is:
1. A thin profile keyboard for a computing device, comprising: a
plurality of baseplates arranged in a plurality of rows; and a
plurality of keys, each of the plurality of keys associated with
one of the plurality of baseplates, wherein the plurality of keys
associated with a first baseplate are offset from the plurality of
keys associated with a second baseplate, each key comprising: a key
cap; an actuator attached to the respective baseplate, the actuator
being configured to deform to activate electrical switch circuitry;
and a rigid support lever having a first end attached to a bottom
surface of the key cap and a second end attached to a substrate at
a pivot point, wherein a portion of the support lever is positioned
over the actuator and wherein when a force is applied to a top
surface of the key cap, the force causes the support lever to
rotate about the pivot point, causing a bottom surface of the
support lever to contact and deform the actuator, wherein the rigid
support lever at least partially underlies at least one of the
plurality of baseplates.
2. The keyboard of claim 1, wherein the actuator is a metal dome
for providing a low-travel keystroke having an abrupt force
drop.
3. The keyboard of claim 2, wherein the low-travel keystroke has a
travel distance that is less than about 1.85 mm.
4. The keyboard of claim 2, wherein the low-travel keystroke has a
travel distance that is in a range of about 0.2 mm to about 0.5
mm.
5. The keyboard of claim 1, wherein the top surface of the key cap
is substantially flat and the bottom surface of the key cap is
substantially flat.
6. The keyboard of claim 5, wherein the key cap is formed of
glass.
7. The keyboard of claim 5, wherein the key cap is formed of
metal.
8. The keyboard of claim 1, wherein the support lever comprises an
elastomeric spacer configured to contact the actuator only when the
force is applied to the top surface of the key cap.
9. A method of assembling at least a portion of a low-travel
keyboard for a computing device, comprising: providing a first and
second baseplate; providing a metal dome above the first baseplate,
the metal dome configured to deform when depressed from above,
wherein the metal dome is configured to activate electrical switch
circuitry of the keyboard when the metal dome is deformed;
disposing a support lever over the metal dome, wherein the support
lever is coupled with a substrate at a point on a first end of the
support lever; and adhering a bottom surface of a key cap to a top
surface of a second end of the support lever, wherein the second
end of the support lever is positioned over the metal to deform the
dome when depressed from above; wherein the support lever is
positioned to at least partially underlie the second baseplate.
10. The method of claim 9, wherein the support lever is formed of a
rigid material and pivotally coupled with the substrate, wherein
the support lever is configured to pivot about the point when
depressed from above.
11. The method of claim 9, wherein the support lever is formed of a
flexible material and fixedly attached at the first end to the
substrate.
12. The method of claim 9, further comprising providing a compliant
component on the support lever, wherein the compliant component is
positioned directly over the metal dome and configured to contact
the metal dome when the support lever is depressed from above.
13. The method of claim 9, wherein a total travel distance of the
keyboard is less than 1.85 mm.
14. The method of claim 9, wherein the key cap is formed of a slab
of material.
15. The method of claim 9, wherein the electrical switch circuitry
is in a membrane disposed below the metal dome, wherein the
membrane comprises conductive traces.
16. The method of claim 15, wherein the membrane comprises a top
layer, a spacer layer, and a bottom layer.
17. The method of claim 16, wherein the top layer contacts the
bottom layer when the metal dome is deformed.
18. A thin-profile keyboard for a computing device having a
plurality of key switches arranged in a plurality of rows, each key
switch comprising: a portion of a membrane including electrical
switch circuitry; a metal dome disposed over the membrane and
configured to deform to activate the electrical switch circuitry; a
single support lever having: a first end coupled to a first
substrate; a second end of the support lever disposed over the
metal dome; a first planar segment extending from the first end,
the first planar segment at least partially underlying a second
substrate; a second planar segment extending from the second end;
and a non-planar segment connecting the first end to the second
end; wherein the support lever is configured to deform the metal
dome when the support lever is depressed from above; and a key cap
disposed over and rigidly adhered to the second end of the support
lever.
19. The keyboard of claim 18, wherein the support lever includes an
elastomeric component positioned over the metal dome, wherein the
elastomeric spacer is configured to contact and deform the metal
dome when the support lever is depressed from above.
20. The keyboard of claim 18, wherein the support lever is formed
of a rigid material and is pivotally coupled to the first
substrate.
21. The keyboard of claim 18, wherein the support lever is formed
of a flexible material and is fixedly coupled to the first
substrate.
22. The keyboard of claim 18, wherein the membranes and support
levers are interwoven.
23. The tactile low-travel keyboard of claim 18, wherein the key
cap has a substantially flat top surface and a substantially flat
bottom surface.
24. The keyboard of claim 18, wherein the metal dome comprises
stainless steel.
25. The keyboard of claim 18, wherein some of the support levers
are curved.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The described embodiments relate generally to peripheral devices
for use with computing devices and similar information processing
devices. More particularly, the present embodiments relate a thin
profile, aesthetically pleasing keyboard well suited for use with
computing devices, and methods of assembling such thin profile,
aesthetically pleasing keyboards.
2. Description of the Related Art
The outward appearance, as well as functionality, of a computing
device and its peripheral devices is important to a user of the
computing device. In particular, the outward appearance of a
computing device and peripheral devices, including their design and
heft, is important, as the outward appearance contributes to the
overall impression that the user has of the computing device. One
design challenge associated with these devices, especially with
portable computing devices, generally arises from a number of
conflicting design goals, including the desirability of making the
device attractive, smaller, lighter, and thinner while maintaining
user functionality.
Therefore, it would be beneficial to provide a keyboard for a
portable computing device that is aesthetically pleasing, yet still
provides the stability for each key that users desire. It would
also be beneficial to provide methods for manufacturing the
keyboard having an especially aesthetic design as well as
functionality for the portable computing device.
SUMMARY OF THE DESCRIBED EMBODIMENTS
This paper describes various embodiments that relate to systems,
methods, and apparatus for providing a trapdoor keyboard mechanism
for a low-travel footprint keyboard that allows the use of
aesthetically pleasing key caps and also provides key stability for
use in computing applications.
According to one embodiment, a thin profile keyboard for a
computing device is described. The keyboard includes a plurality of
keys arranged in a plurality of rows. Each row includes a plurality
of keys and the keys in a first row are offset from the keys in a
second row. Each key includes a key cap and an actuator attached to
a base plate. The actuator is configured to deform to activate
electrical switch circuitry when it is deformed. A portion of a
rigid support lever is positioned over the actuator, which can be a
metal dome. The support lever has one end that is attached to a
bottom surface of the key cap and a second end that is attached to
a substrate at a pivot point. When a force is applied to the top
surface of the key cap, the force causes the support lever to
rotate about the pivot point, causing a bottom surface of the
support lever to contact and deform the actuator. In an embodiment,
the key cap can be in the form of a flat slab. An elastomeric
spacer may be provided on the support lever over the metal dome
such that the elastomeric spacer deforms the metal dome when the
key is depressed by a user. The use of a single support lever
allows the key cap to be simply adhered to the support lever and
the support lever also reduces instability when the key is
depressed by a user. As the key cap can be adhered to the support
lever, intricate attachment features on the underside of the key
cap are unnecessary, thereby allowing the key cap to be formed of a
variety of materials, including glass and metal.
A method of assembling at least a portion of a low-travel keyboard
for a computing device is disclosed. The method can be carried out
by the following operations: providing a metal dome configured to
deform when depressed from above, disposing a support lever over
the metal dome, and adhering a key cap to the support lever. The
metal dome can activate electrical switch circuitry of the keyboard
when the metal dome is deformed. The support lever is coupled with
a substrate at a point on a first end of the support lever. The
bottom of the key cap is adhered to a top surface of the second end
of the support lever, which is positioned over the metal dome to
deform the dome when depressed from above. In an embodiment, the
support lever is formed of a rigid material and is pivotally
coupled to the substrate such that the support lever deforms the
metal dome when the support lever is depressed from above, as the
support lever rotates slightly about the pivot point where it is
coupled to the substrate. In another embodiment, the support lever
is formed of a flexible material and fixedly coupled to the
substrate on one end.
Other aspects and advantages of the invention will become apparent
from the following detailed description taken in conjunction with
the accompanying drawings which illustrate, by way of example, the
principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be readily understood by the following detailed
description in conjunction with the accompanying drawings, wherein
like reference numerals designate like structural elements, and in
which:
FIG. 1 is a side view of a typical key switch of a scissor-switch
keyboard.
FIG. 2 is a side view of an embodiment of a key having a single
support lever.
FIG. 3 is a detailed view of an embodiment of the pivoted
attachment of the support lever to the topcase.
FIG. 4 is a simplified top perspective view of a key cap 210
positioned in an embodiment of the topcase.
FIG. 5 is a bottom plan view of an embodiment of a keyboard
arrangement.
FIG. 6 is a detailed perspective view of the bottom of the keyboard
arrangement shown in FIG. 5.
FIG. 7 is a detailed perspective view of an embodiment of a
three-layer membrane of a printed circuit board.
FIG. 8 is a flow chart of a method of assembling an embodiment of a
key switch having a single support lever.
DETAILED DESCRIPTION OF SELECTED EMBODIMENTS
Reference will now be made in detail to representative embodiments
illustrated in the accompanying drawings. It should be understood
that the following descriptions are not intended to limit the
embodiments to one preferred embodiment. To the contrary, it is
intended to cover alternatives, modifications, and equivalents as
may be included within the spirit and scope of the described
embodiments as defined by the appended claims.
The embodiments herein relate to a thin profile peripheral input
device that is both efficient and aesthetically pleasing. In
particular, the thin profile peripheral input device can take the
form of a keyboard that can include at least a low profile key cap
assembly. The low profile key cap assembly can, in turn, be formed
of a key cap connected to one end of a beam or lever, the beam or
lever having another end pivotally connected to base portion. The
key cap can be positioned proximate to a switch mechanism that can
be engaged by the key cap impinging thereupon. In one embodiment,
the beam can be rigid in nature and formed of, for example,
stainless steel, aluminum, or any other suitable material. The
rigid beam can be pivotally connected to the base portion at a
pivot point using, for example, bushings. In this way, in order to
engage the actuator, a force can be applied to the key cap causing
the beam and the key cap to rotate about the pivot point resulting
in the key cap moving in an arc-like manner. However, due to the
relatively long distance between the pivot point and the key cap
and the reduced Z stack of the key cap assembly, the angle of
rotation of the key cap is small enough and any rotational wobble
is substantially reduced.
In another embodiment, the beam can be formed of a more compliant
material fixedly connected to the base. In this way, when the force
is applied to the key cap, the beam can bend allowing a more
compliant feel to the key cap. It should be noted that, in some
cases, a compliant material layer formed of, for example, silicone
rubber can be positioned between the key cap and the actuator
providing a distinctive feel to the key cap. In some cases, this
distinctive feel can be customized to a particular application by
using various materials. For example, a harder material can provide
a more firm feel whereas softer, more compliant materials, such as
silicone rubber, a more compliant feel. In this way, it is
contemplated that selected key cap assemblies can be fashioned to
have their own associated "feel" that can depend upon a number of
factors such as a position on the keyboard, function associated
with key cap, and so on.
Furthermore, since there is no restriction on the material used to
form an observable portion of the key cap, the key caps can be
formed to include an upper layer formed of materials heretofore
deemed unsuitable for use in keyboards. Such materials as wood,
stone, polished meteorite (watch dials have been made from polished
meteorite), glass, etc. can be used as opposed to standard key caps
that rely on plastic material.
There are several types of keyboards, usually differentiated by the
switch technology employed in their operation. The choice of switch
technology affects the keys' responses (i.e., the positive feedback
that a key has been depressed) and travel (i.e., the distance
needed to push the key to enter a character reliably). One of the
most common keyboard types is a "dome-switch" keyboard, which works
as described below. When a key is depressed, the key pushes down on
a rubber dome sitting beneath the key. The rubber dome collapses,
which gives tactile feedback to the user depressing the key, and
causes a pair of conductive lines on the printed circuit board
(PCB) below the dome to contact, thereby closing the switch. A chip
in the keyboard emits a scanning signal along the pairs of lines on
the PCB to all the keys. When the signal in one pair of lines
changes due to the contact, the chip generates a code corresponding
to the key connected to that pair of lines. This code is sent to
the computer either through a keyboard cable or over a wireless
connection, where it is received and decoded into the appropriate
key. The computer then decides what to do based on the particular
key depressed, such as display a character on the screen, or
perform some other type of action. Other types of keyboards operate
in a similar manner, with the main difference being how the
individual key switches work. Some examples of other keyboards
include capacitive keyboards, mechanical-switch keyboards,
Hall-effect keyboards, membrane keyboards, roll-up keyboards, and
so on.
FIG. 1 is a side view of a typical key switch 100 of a
scissor-switch keyboard. A scissor-switch keyboard is a type of
relatively low-travel dome-switch keyboard that provides the user
with good tactile response. Scissor-switch keyboards typically have
a shorter total key travel distance, which is about 1.5-2 mm per
key stroke instead of about 3.5-4 mm for standard dome-switch key
switches. Thus, scissor-switch type keyboards are usually found on
laptop computers and other "thin-profile" devices. The
scissor-switch keyboards are generally quiet and require relatively
little force to press.
As shown in FIG. 1, the key cap 110 is attached to the base plate
or PCB 120 of the keyboard via a scissor-mechanism 130. The
scissor-mechanism 130 includes two separate pieces that interlock
in a "scissor"-like manner, as shown in FIG. 1. The
scissor-mechanism 130 is typically formed of a rigid material, such
as plastic or metal or composite material, as it provides
mechanical stability to the key switch 100. As illustrated in FIG.
1, a rubber dome 140 is provided. The rubber dome 140, along with
the scissor-mechanism 130, supports the key cap 110.
When the key cap 110 is pressed down by a user in the direction of
arrow A, it depresses the rubber dome 140 underneath the key cap
110. The rubber dome 140, in turn, collapses, giving a tactile
response to the user. The scissor-mechanism 130 also transfers the
load to the center to collapse the rubber dome 140 when the key cap
110 is depressed by the user. The rubber dome also dampens the
keystroke in addition to providing the tactile response. The rubber
dome 140 can contact a membrane 150, which serves as the electrical
component of the switch. The collapsing rubber dome 140 closes the
switch when it depresses the membrane 150 on the PCB, which also
includes a base plate 120 for mechanical support. The total travel
of a scissor-switch key is shorter than that of a typical rubber
dome-switch key. As shown in FIG. 1, the key switch 100 includes a
three-layer membrane 150 (on a PCB) as the electrical component of
the switch. The membrane 150 can be a three-layer membrane or other
type of PCB membrane, which will be described in more detail
below.
The following description relates to a single support lever
keyboard mechanism for a low-travel keyboard suitable for a small,
thin-profile computing device, such as a laptop computer, netbook
computer, desktop computer, etc. The use of a single support lever
to support the key cap and to activate the switch circuitry not
only allows for the key cap to be formed of almost any material but
also provides stability to each key, as will be described in more
detail below. The aesthetic appearance of a keyboard therefore
depends greatly on the key caps, which form most of the visible
portion of a keyboard. It will be understood that the material of
the key caps will be important, not only because the key caps are
highly visible but also because the material should have a desired
tactile feel to a user's fingers.
These and other embodiments of the invention are discussed below
with reference to FIGS. 2-8. However, those skilled in the art will
readily appreciate that the detailed description given herein with
respect to these figures is for explanatory purposes as the
invention extends beyond these limited embodiments.
FIG. 2 is a side view of an embodiment of a key switch 200. As
shown in FIG. 2, the key cap 210 in this embodiment is different
from standard key caps like the one shown in FIG. 1. The key cap
210 of this embodiment can be a slab of material that is flat. In
other words, the key cap has a substantially flat top surface and a
substantially flat bottom surface. The key cap 210 does not need to
have any features on the underside for attaching any other
components of the key 200. The key cap 210 can simply be adhered to
a support lever 220. In an embodiment, the key cap 210 can be
adhered to the support lever 220 with an adhesive, such as VHB.TM.
double-sided bonding tape, available from 3M Company of St. Paul,
Minn.
The keyboard can include a key cap 210, such as the one shown in
FIG. 2, positioned over and rigidly attached to a support lever
220. According to embodiments described herein, the key cap 210 can
be formed of almost any suitable material, including, but not
limited to, wood, stone, polished meteorite, ceramic, metal, and
glass. An outer surface of the key cap can also be coated with a
non-slip material, such as rubber. The key cap 210 can have a
thickness in a range of about 0.5-1 mm. In one embodiment, a glass
key cap has a thickness of about 1 mm. According to another
embodiment, a ceramic key cap has a thickness of about 0.5 mm. It
will be appreciated that the thickness of the key cap 210 may
depend on the material of the key cap 210. In some embodiments, the
top surface of the key cap 210 is surface-marked. In other
embodiments, the key cap 210 can be laser-cut, two-shot molded,
engraved, or formed of transparent material with printed inserts
215.
A standard key, such as the one shown in FIG. 1, has a key cap 110
typically formed of a molded plastic material so that the underside
of the key cap 110 can include intricate features for attaching the
scissor mechanism 130. As described in more detail below, the key
cap 210 in the described embodiments can be in the form of a flat
slab that is adhered to a support lever 220. Thus, the key cap 210
need not be formed of a moldable plastic material to accommodate
intricate attachment features for a scissor mechanism. Instead, the
key cap 210 can be formed of other materials, including, but not
limited to, glass, wood, stone, and polished meteorite.
According to one embodiment, the support lever 220 can be formed of
a rigid material, such as stainless steel or ceramic. Stainless
steel has a number of characteristics that make it a good choice
for the support lever 220. For example, stainless steel is rigid,
durable and fairly resistant to corrosion, and it is a relatively
inexpensive metal that can be easily machined and has well known
metallurgical characteristics. Furthermore, stainless steel can be
recycled. According to an alternative embodiment, the support lever
220 is formed of a ceramic material.
According to some embodiments, the support lever 220 is fixedly
attached at one end to the underside of the key cap 210. The fixed
attachment provides rotational stability to the key 200 because
there is essentially only one moving part when the key cap 210 is
depressed by a user. In other words, the support lever 220 and the
attached key cap 210 together form the single moving part. A
standard key, such as the one shown in FIG. 1, typically has three
moving parts: the key cap 110 and the two linked parts of the
scissor mechanism 130.
The rigid support lever 220 provides stability to the key by
reducing wobble from side to side. The key 200 may rotate slightly
forward when depressed, which may be ergonomically desirable.
However, such slight rotation is virtually imperceptible for
low-travel keys, as is described in more detail below. As shown in
FIG. 2, a single support lever 220 supports the key cap 210.
The support lever 220, which, on one end, has its top surface
attached to the underside of the key cap 210, can also dictate the
height of the key cap 210 or the distance between the key cap 210
and the base plate 270. In the embodiment shown in FIG. 2, the
support lever 220 has an upper portion in a plane and a lower
portion in a lower plane, and the upper portion and the lower
portion are connected by a portion in a plane perpendicular to the
planes of the upper and lower portions. The other end of the
support lever 220, which is on the lower portion, is pivotally
coupled with the topcase 260, as described in more detail below. It
will be understood that the topcase 260 is the portion of the
housing or substrate surrounding the keys. In the event the key cap
210 is depressed in an off-center manner, the support lever 220
transfers the load to the center of the key. According to an
embodiment, the support lever 220 is formed of steel and has a
thickness of about 0.5 mm.
In this embodiment, the support lever 220 is formed of a rigid
material and rotatably or pivotally coupled, at its other lower
end, with the topcase 260 at a pivot point at a distance from the
key cap 210. In some embodiments, the distance is about one key
pitch. As illustrated in FIG. 2, a bearing 222 is positioned at the
lower end of the support lever 220. The distance between the
bearing 222 and the key cap 210 can be dictated by the pitch
between the rows of keys. As the skilled artisan will appreciate,
the distance, and therefore the length of the support lever 220,
can be limited by the space available and depends on the size of
the device and the individual key caps 210. In some embodiments,
the distance between the bearing 222 and the key cap 210 can be in
a range of about 25-30 mm. As shown in FIG. 2, the bearings 222 are
positioned underneath the topcase 260 of the device.
As shown in FIG. 2, the end of the support lever 220 that is
attached to the key cap 210 is higher than the end that is
pivotally coupled with the topcase 260 at the bearing 222. In the
embodiment shown in FIG. 2, the bearings 222 are integrally formed
with the support lever 220. In other embodiments, the bearings 222
can be rigidly attached to the support lever 220. The skilled
artisan will understand that such a configuration of the support
lever 220 and the attachment of the key cap 210 to a single support
lever 220 allows the support lever 220 to rotate slightly when the
key cap 210 is pushed down by a user. In an embodiment where the
bearing 222 is located closer to the user than the key 200, the
support lever 220 will rotate slightly forward when the key cap is
depressed. Such a forward rotation during key travel can be
ergonomically desirable. For low travel keyboards, such rotation
can be almost imperceptible.
According to some embodiments, the keys 200 are low-travel keys
that have a total travel in a range of about 0.2 mm to about 1.85
mm. In other embodiments, the keys have a total travel in a range
of about 0.2 mm to about 0.5 mm.
FIG. 3 is a detailed view of an embodiment of the pivoted coupling
of the support lever 220 to the topcase 260. In this embodiment,
the support lever 220 has a pair of bearings 222 through which a
dowel pin 230 threaded. According to this embodiment, the dowel pin
230 acts as the pivot axis about which the support lever 220 pivots
or rotates. In an embodiment, the dowel pin 230 can be fixedly
coupled to the topcase 260 using snaps that trap the dowel pin 230
in its bearing such that it can simply be pressed in during
assembly. In another embodiment, the bearings can be pressed onto
the ends of the dowel pin 230 and the assembly of the dowel pin 230
and two bearings can be trapped in a recess in the topcase 260.
According to some embodiments, the dowel pin 230 can have a
diameter in a range of about _ mm to _ mm. In one embodiment, the
dowel pin 230 has a diameter of about 0.8 mm.
According to another embodiment, the support lever 220 is formed of
a flexible material that can be fixedly adhered to the underside of
the key cap 210 on its upper end and is fixedly attached to the
topcase 260 at the lower end. In this embodiment, the support lever
220 can be formed of spring steel and does not rotate about a pivot
point. Instead, the flexible nature of the support lever material
allows a similar motion when the key is depressed, like a linear
flex-spring.
As shown in FIG. 2, the support lever 220 can include a compliant
component, such as an elastomeric spacer 225, between the key cap
210 and a metal dome 240 positioned underneath the elastomeric
spacer 225. The elastomeric spacer 225 may be formed of an
extremely compliant material, such as rubber or silicone rubber.
The compliant nature of the elastomeric spacer 225 can provide a
desirable and distinctive feel to the user when the key is
depressed. The elastomeric spacer 225 also reduces rattle of the
keyboard by being in constant mild compression and also improves
overall sensitivity to tolerance variation during assembly. As
described in more detail below, the elastomeric spacer 225 contacts
and collapses the metal dome 240 to activate the switch circuitry.
The metal dome 240 therefore acts as an actuator.
As illustrated in FIG. 2, a metal dome 240 is positioned over the
membrane 250 and the base plate 270. The metal dome 240 can be
formed of a material, such as stainless steel. As noted above,
stainless steel is durable and fairly resistant to corrosion, and
it is a relatively inexpensive metal that can be easily machined
and has well known metallurgical characteristics. In some
embodiments, the stainless steel metal dome can be plated with
gold, silver, or nickel.
The skilled artisan will appreciate that it is desirable to make
the keyboard (and computing device) thinner, but users still want
the tactile feel to which users are accustomed. It is desirable for
the keys to have some "bounce-back" or "snappy" feel. As can be
appreciated by the skilled artisan, substantially flat keyboards,
such as membrane keyboards, do not provide the tactile feel that is
desirable for a keyboard. Similarly, simply reducing the travel of
a typical rubber dome scissor-switch keyboard also reduces the
tactile or "snappy" feel that a conventional dome-switch keyboard
provides.
Metal domes can provide very low travel as well as a crisp tactile
feel. Like a rubber dome, a metal dome also dampens the keystroke
in addition to providing a very crisp tactile response to the user.
A metal dome typically has a good tactile force drop with a
relatively short travel distance, which is typically about 0.1-0.2
mm.
The skilled artisan will appreciate that a metal dome has a quick
force drop over a short travel distance relative to an elastomeric
dome. Elastomeric domes lack the quick force drop and therefore the
crisp snap of metal domes. Thus, elastomeric domes do not provide
the positive crisp tactile response of metal domes, especially when
the amount of travel is reduced. However, although a metal dome can
provide a positive crisp tactile feel, a metal dome alone cannot
provide the desired tactile feel and travel distance for a keyboard
suitable for typing or otherwise inputting text. The skilled
artisan will appreciate that a metal dome cannot achieve travel
greater than about 0.7 mm, as the metal is difficult to deform and
would require a large amount of force for deformation. Even if
enough force were applied to the metal dome, it would not be able
to achieve a travel distance greater than about 0.7 mm unless the
metal dome is quite large. A larger metal dome would cause each
individual key to also be quite large, which can be undesirable and
impractical, especially in portable devices.
According to some embodiments, the support lever 220 can be
provided with an elastomeric spacer 225, as shown in FIG. 2. The
elastomeric spacer 225 can be positioned over a metal dome 240 such
that the elastomeric spacer 225 contacts the top surface of the
metal dome 240 when the key cap 210 is depressed by a user. The
elastomeric spacer 225 can be formed of a compliant material, such
as silicone rubber, and increases the travel distance of the key
200. As discussed above, the metal dome 240 typically has a
relatively short travel distance, but provides crisp, tactile
feedback to the user, but the elastomeric spacer 225 can increase
the travel distance, which can be desirable, and also provide the
tactile feedback to which users have become accustomed. Thus, the
combination of the elastomeric spacer 225 with the metal dome 240
allows the key to have a low-travel distance while maintaining the
positive tactile feedback that is desirable for a keyboard. The
elastomeric spacer 225 also allows for easier assembly of the keys
200, as the assembly tolerance is less sensitive with the inclusion
of the elastomeric spacer 225. The elastomeric spacer 225 also
provides the further benefit of reducing rattling in the
keyboard.
As shown in FIG. 2, the metal dome 240 is substantially concave or
hemispherical and oriented with the vertex of each of the dome
being at the highest point. In other words, the metal dome opening
is facing downward. As the dome 240 is concave, it is a
normally-open tactile switch. The switch only closes when the dome
240 is collapsed, as will be described in more detail below.
In this embodiment, the elastomeric spacer 225 also provides the
ability for longer travel. The metal dome 240 provides the majority
of the tactile force drop and also activates the switch circuitry
of the membrane 250 on the base plate 270. The abrupt or quick
force drop of the metal dome 240 provides the crisp "snappy" feel
for the user. It provides the kind of force drop that the metal
dome allows, and also the initial compliancy and force build-up
that are absent in metal domes.
When a user presses down on the key cap 210, it causes the support
lever 220 to which the key cap 210 is rigidly attached to rotate
slightly and move downward. As the support lever 220 moves
downward, the elastomeric spacer 225 contacts and collapses the
elastomeric dome 220. As shown in FIG. 2, the elastomeric spacer
225 is positioned directly over the center of the top of the metal
dome 240. Thus, when the support lever 220 moves downward, the
elastomeric spacer 225 then contacts and pushes down on the center
of the top of the metal dome 240, and collapses the metal dome 240.
As shown in FIG. 2, the elastomeric spacer 225 does not contact the
metal dome 240 when the key cap 210 is not depressed. The underside
of the center of the collapsing metal dome 240 contacts the top
side of the top layer 252 (FIG. 7) of the membrane 250, thereby
causing the contact pads 258 of the circuit traces (FIG. 7) on the
top layer 252 (FIG. 7) and the bottom layer 256 (FIG. 7) of the
membrane 250 to connect and close the switch, which completes the
connection to enter the character. As shown in FIG. 2, the membrane
250 is secured to a base plate or PCB 270.
According to an embodiment, the support lever 220 has a thickness
of about 0.5 mm. In other embodiments, the support lever may have a
thickness that is less than 0.5 mm. In some embodiments, the
elastomeric spacer can have a thickness in a range of about 0.3 to
1 mm. In other embodiments, the elastomeric spacer can have a
thickness in a range of about 0.5 to 1 mm. The metal dome 240 can
have a height in a range of about 0.3 mm to about 0.7 mm. According
to another embodiment, the metal dome 240 has a height in a range
of about 0.3 mm to about 0.5 mm. In still another embodiment, the
metal dome 240 has a height in a range of about 0.5 mm to about 0.7
mm.
In an embodiment, the metal dome 240 has a thickness in a range of
about 0.03 mm to about 0.1 mm. It will be understood that the metal
dome 240 typically has a uniform thickness if it is formed from a
sheet of metal. The skilled artisan will appreciate that the
thicknesses of the dome 240 and elastomeric spacer 225 can be
adjusted and/or varied to obtain the desired force drop. The base
diameter of the dome 240 can be in the range of about 3 mm to 7
mm.
According to an embodiment, as shown in FIG. 2, the metal dome 240
can be secured, at its base in its non-concave portions, to the
membrane 250 by means of adhesive, including pressure-sensitive
adhesive tape. In an alternative embodiment, the metal dome 240 is
not adhered to the membrane 250, but is instead encapsulated by an
additional membrane sheet that extends over the metal dome 240 and
is adhered to the membrane 250.
FIG. 4 is a simplified top perspective view of a key cap 210
positioned in an embodiment of the topcase 260. For simplicity,
FIG. 4 shows only a single key cap 210 and only a portion of the
topcase 260. As illustrated, keys are positioned in the topcase 260
of this embodiment in a staggered manner. That is, the rows of keys
can be slightly shifted so that keys in one row are not positioned
directly below the keys in the row above. The skilled artisan will
appreciate that the keys can be arranged in any manner that is
desired.
FIG. 5 is a bottom plan view of an embodiment of a keyboard
arrangement. FIG. 6 is a detailed perspective view of the bottom of
the keyboard arrangement shown in FIG. 5. As shown in FIG. 5, the
base plate 270 is arranged in rows across the keyboard. The base
plate 270 can be a rigid printed circuit board (PCB). As shown in
the embodiments of FIGS. 5 and 6, the base plate 270 and the
support levers 220 can be interwoven. It will be understood that
the keys 200 of the keyboard can be arranged in any manner that is
desired and that the components of the keys 200 can similarly be
arranged in any manner such that they fit in the available space.
For example, the support lever 220 for some keys can be curved, as
illustrated in FIG. 5, to accommodate the different positions of
the keys and to conform to an existing keyboard arrangement.
FIG. 7 is a detailed perspective view of an embodiment of the
membrane 250. According to an embodiment, the membrane 250 can have
three layers, including a top layer 252, a bottom layer 256, and a
spacer layer 254 positioned between the top layer 252 and the
bottom layer 256. The top layer 252 and the bottom layer 256 can
include conductive traces and their contact pads 258 on the
underside of the top layer 252 and on the top side of the bottom
layer 256, as shown in FIG. 7. The conductive traces and contact
pads 258 can be formed of a metal, such as silver or copper. As
illustrated in FIG. 7, the membrane sheet of the spacer layer 254
includes voids 260 to allow the top layer 252 to contact the bottom
layer 256 when the metal dome 240 is collapsed. According to an
embodiment, the top layer 252 and bottom layer 256 can each have a
thickness of about 0.075 .mu.m. The spacer layer 254 can have a
thickness of about 0.05 .mu.m. The membrane sheets forming the
layers of the membrane 250 can be formed of a plastic material,
such as polyethylene terephthalate (PET) polymer sheets. According
to an embodiment, each PET polymer sheet can have a thickness in
the range of about 0.025 mm to about 0.1 mm.
Under "normal" conditions when the key pad is not depressed by a
user (as shown on the left side of FIG. 7), the switch is open
because the contact pads 258 of the conductive traces are not in
contact. However, when the top layer 252 is pressed down by the
metal dome 240 in the direction of arrow A (as shown on the right
side of FIG. 7), the top layer 252 makes contact with the bottom
layer 256. The contact pad 258 on the underside of the top layer
252 can then contact the contact pad 258 on the bottom layer 256,
thereby allowing the current to flow. The switch is now "closed",
and the computing device can then register a key press, and input a
character or perform some other operation. It will be understood
that other types of switch circuitry can be used instead of the
three-layer membrane 250 described above.
A process for assembling the key switch 200, such as the one shown
in FIG. 2, will be described with reference to FIG. 8. A process
for assembling the components of the key switch 200 will be
described below with reference to steps 800-870. In step 800, a
base plate 270 is provided for mechanical support for the PCB as
well as the entire key switch 200. In one embodiment, the base
plate 270 is formed of stainless steel. In other embodiments, the
base plate 270 can be formed of aluminum. According to an
embodiment, the base plate 270 has a thickness in a range of about
0.2 mm to about 0.5 mm.
A process for forming the three-layer membrane 250 on the base
plate 270 will be described below with reference to steps 810-830.
In step 810, the bottom layer 256 of the membrane 250 can be
positioned over the base plate 270. Next, in step 820, the spacer
layer 254 can be positioned over the bottom layer 256 such that the
voids 260 are in the areas of the contact pads 258. In step 830,
the top layer 252 can be positioned over the spacer layer 254 such
that the contact pads 258 on the underside of the top layer 252 are
positioned directly over the contact pads 258 on top side of the
bottom layer 256 so that they can contact each other when the metal
dome 240 is deformed. The layers 252, 254, 256 can be laminated
together with adhesive. It will be understood that steps 810-830
can be combined into a single step by providing a three-layer
membrane 250 that is pre-assembled or pre-laminated. The membrane
250 is positioned over the base plate 270 and held in place by one
or more other components of the key switch 200, such as the scissor
mechanism 230.
According to this embodiment, in step 840, the metal dome 240 can
be attached to the top side of the top layer 252 of the membrane
250 such that the concave dome portion is positioned over the
contact pads 258 and the void 260. In step 850, the support lever
220 is positioned over the metal dome such that the elastomeric
spacer 225 is positioned directly over the center of the metal dome
240. In step 860, the support lever 220 is coupled to the topcase
260 at a point at a distance from the key switch 200. In an
embodiment, the support lever 220 may be formed of a rigid material
and has bearings 222 and the support lever 220 is pivotally
coupled, at one end, to the topcase 260 at the point so that the
support lever 220 can rotate slightly when a downward force is
applied from above. In another embodiment, the support lever 220
may be formed of a flexible material and is fixedly coupled, at one
end, to the topcase 260. In this embodiment, in step 870, to
complete the key switch 200, the key cap 210 is positioned over and
attached to the support lever 220. According to an embodiment, the
underside of the key cap 210 can be adhered to the top side of the
support lever 220.
The advantages of the invention are numerous. Different aspects,
embodiments or implementations may yield one or more of the
following advantages. One advantage of the invention is that a
low-travel keyboard yet may be provided for a thin-profile
computing device without compromising the tactile feel of the
keyboard.
The many features and advantages of the described embodiments are
apparent from the written description and, thus, it is intended by
the appended claims to cover such features and advantages. Further,
since numerous modifications and changes will readily occur to
those skilled in the art, the invention should not be limited to
the exact construction and operation as illustrated and described.
Hence, all suitable modifications and equivalents may be resorted
to as falling within the scope of the invention.
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